hi ,not to be pickey ,but your post makes little sence to meanyway! ,please try explaining it a little better ,like what you actually meany by this ,"its showing unknown program icon for all other programs"what dose a unkown program icon look like ,what is meant by a all other programs ,the use of the word others implies that some icons work!

Acording to me the explorer.exe file might have been damaged and hence I would recommend that you try to repair the windows registry using your windows installation disc. This could be due to a virus but can't remember th name of it.